Sometimes the due dates estimated by an early ultrasound don't match the expected due date based on the last menstrual period. Learn why. When will I have my dating scan? How accurate are dating scans? What else will the dating scan reveal? What happens at a dating scan? How big will my baby. Women's perception of accuracy of ultrasound dating in late the last menstrual period (LMP) and a prediction from obstetric ultrasound scan.
Date changes for smaller discrepancies 10—14 days are appropriate based on how early in this second-trimester range the ultrasound examination was performed and on clinician assessment of LMP reliability.
Because of the risk of redating a small fetus that may be growth restricted, management decisions based on third-trimester ultrasonography alone are especially problematic; therefore, decisions need to be guided by careful consideration of the entire clinical picture and may require close surveillance, including repeat ultrasonography, to ensure appropriate interval growth. The best available data support adjusting the EDD of a pregnancy if the first ultrasonography in the pregnancy is performed in the third trimester and suggests a discrepancy in gestational dating of more than 21 days.
Conclusion Accurate dating of pregnancy is important to improve outcomes and is a research and public health imperative. As soon as data from the LMP, the first accurate ultrasound examination, or both are obtained, the gestational age and the EDD should be determined, discussed with the patient, and documented clearly in the medical record.
Predicting delivery date by ultrasound and last menstrual period in early gestation.
The American College of Obstetricians and Gynecologists, the American Institute of Ultrasound in Medicine, and the Society for Maternal—Fetal Medicine recognize the advantages of a single dating paradigm being used within and between institutions that provide obstetric care. Table 1 provides guidelines for estimating the due date based on ultrasonography and the LMP in pregnancy, and provides single-point cutoffs and ranges based on available evidence and expert opinion. Fetal Imaging Workshop Invited Participants.
A comparison of recalled date of last menstrual period with prospectively recorded dates. J Womens Health Larchmt ; Comparison of pregnancy dating by last menstrual period, ultrasound scanning, and their combination.
When to have dating scan
Am J Obstet Gynecol ; Last menstrual period versus ultrasound for pregnancy dating. Int J Gynaecol Obstet ; First trimester ultrasound screening is effective in reducing postterm labor induction rates: Ultrasound for fetal assessment in early pregnancy. Cochrane Database of Systematic ReviewsIssue 7. Predicting delivery date by ultrasound and last menstrual period in early gestation. New charts for ultrasound dating of pregnancy and assessment of fetal growth: Ultrasound Obstet Gynecol ; First- and second-trimester ultrasound assessment of gestational age.
First- vs second-trimester ultrasound: Br J Obstet Gynaecol ; Gestational age in pregnancies conceived after in vitro fertilization: Ultrasound dating at 12—14 weeks of gestation.Can a baby's due date be a month off when determined by an ultrasound?
A prospective cross-validation of established dating formulae in in-vitro fertilized pregnancies. Accuracy of gestational age estimation by means of fetal crown—rump length measurement. Estimation of gestational age by transvaginal sonographic measurement of greatest embryonic length in dated human embryos.
Ultrasound Obstet Gynecol ;4: Underestimation of gestational age by conventional crown—rump length dating curves. New crown—rump length curve based on over pregnancies. Standardization of sonar cephalometry and gestational age. Sonographic prediction of gestational age: Conceptional age, menstrual age, and ultrasound age: American College of Obstetricians and Gynecologists. Computer assisted analysis of fetal age in the third trimester using multiple fetal growth parameters. Antenatal health education should discourage self-referral for ultrasound scan dating and emphasize its limitations in late pregnancy as well as the perinatal effects of prolonged pregnancy.
Both are important for optimal prenatal, intrapartum, and postnatal care. For instance, reliable information about gestational age and EDD is useful in assessment of fetal growth during the antenatal period. In clinical practice, the gestational age and EDD are often determined using the LMP, except when the discrepancy between the LMP-derived gestational age or EDD and that of early pregnancy ultrasound scan exceeds 1 week; in this situation, the ultrasound scan estimates are more reliable and should be used.
Further, the rate of post-term pregnancy has been shown to decrease when early ultrasound scan is used in estimating the gestational age and EDD. The uncontrolled proliferation of ultrasound in Nigeria has further heightened the conflict between these two estimates of delivery date because pregnant women are increasingly having access to ultrasound scanning manned by various cadres of health workers, without information on its known limitations. This scenario is a big challenge in terms of prevention of prolonged pregnancy in our environment where women register late for antenatal care 9 and rarely have reliable early ultrasound scan results.
A scenario is often created where the attending medical practitioner feels the pregnancy is prolonged based on a certain LMP-derived EDD while the client holds a different view based on her ultrasound scan-derived EDD, and therefore refuses to accept induction of labor despite counseling.
Methods for Estimating the Due Date - ACOG
The aim of this study was to determine the perception and acceptability of menstrual dating EDD derived from LMP for timing of labor induction for postdatism by pregnant women who have a late pregnancy ultrasound scan. Materials and methods Study area Enugu State is one of the five states in the southeast geopolitical zone of Nigeria, and its capital city is Enugu. It has an average annual temperature of The state covers a land area of approximately 8, The Enugu State University Teaching Hospital, Parklane, is a state-owned teaching hospital located in the center of the Enugu metropolis.
Both centers provide antenatal and postnatal care services to pregnant women in Enugu State. The commonest indication for induction of labor in the two hospitals and in our environment is prolonged pregnancy. Every singleton pregnant woman due for a routine delivery planning discussion at a gestational age of 36 weeks and beyond was eligible for the study.
Exclusion criteria included uncertainty of date, presence of contraindications to vaginal delivery, irregular menstrual cycle prepregnancy, use of hormonal contraceptives prior to pregnancy, or bleeding during pregnancy. After individual counseling of eligible participants, pretested structured questionnaires were administered to consecutive consenting women by trained medical interns.